87561781 has 4 divisors (see below), whose sum is σ = 92712492. Its totient is φ = 82411072.

The previous prime is 87561751. The next prime is 87561797. The reversal of 87561781 is 18716578.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18716578 = 2 ⋅9358289.

It can be written as a sum of positive squares in 2 ways, for example, as 77264100 + 10297681 = 8790^2 + 3209^2 .

It is a cyclic number.

It is not a de Polignac number, because 87561781 - 2⁷ = 87561653 is a prime.

It is a super-2 number, since 2×87561781² = 15334130983783922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (87561731) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2575330 + ... + 2575363.

It is an arithmetic number, because the mean of its divisors is an integer number (23178123).

Almost surely, 2^87561781 is an apocalyptic number.

It is an amenable number.

87561781 is a deficient number, since it is larger than the sum of its proper divisors (5150711).

87561781 is a wasteful number, since it uses less digits than its factorization.

87561781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5150710.

The product of its digits is 94080, while the sum is 43.

The square root of 87561781 is about 9357.4452175794. The cubic root of 87561781 is about 444.0564631410.

The spelling of 87561781 in words is "eighty-seven million, five hundred sixty-one thousand, seven hundred eighty-one".